Canine cranial cruciate ligament deficient stifle biomechanics associated with extra-articular stabilization predicted using a computer model.

OBJECTIVE: To evaluate lateral fabellotibial suture (LFTS) and TightRope CCL (TR) extra-articular stabilization biomechanics in the cranial cruciate ligament (CrCL)-deficient canine stifle joint during the stance phase of gait. STUDY DESIGN: Computer simulations. ANIMALS: Healthy 33-kg Golden Retriever. METHODS: LFTS and TR were implemented in a previously developed 3-D quasi-static rigid body CrCL-deficient canine pelvic limb computer model simulating the stance phase of gait. Ligament loads, relative tibial translation, and relative tibial rotation were determined and compared across the CrCL-intact, CrCL-deficient, and extra-articular stabilized stifle joints. RESULTS: Compared to the CrCL-intact stifle, peak caudal cruciate and lateral collateral ligament (LCL) loads were increased in the LFTS-managed stifle, peak caudal cruciate and LCL loads were decreased in the TR-managed stifle, and peak medial collateral and patellar ligament (PL) loads were similar for both techniques. Compared to the CrCL-deficient stifle, peak caudal cruciate, lateral collateral, and medial collateral ligament loads decreased, and peak PL load was similar in the LFTS- and TR-managed stifle joints. Peak relative tibial translation decreased, and peak relative tibial rotation changed from internal rotation to external rotation in the LFTS- and TR-managed stifle joints compared to the CrCL-deficient stifle. CONCLUSION: Our computer model predicted controlled tibial translation, decreased cruciate and collateral ligament loads, and a change in femorotibial rotation from internal to external with LFTS and TR stifle management as compared to the CrCL-deficient stifle. This study demonstrates how computer modeling can be used to evaluate biomechanics of stifle stabilization surgical techniques.

Canine Stifle Biomechanics Associated With a Novel Extracapsular Articulating Implant Predicted Using a Computer Model.

OBJECTIVE: To evaluate the influence of the Simitri Stable in Stride™ extracapsular articulating implant (EAI) on canine stifle biomechanics in the cranial cruciate ligament (CrCL)-deficient stifle using a 3-dimensional (3D) quasi-static rigid body canine pelvic limb computer model simulating the stance phase of gait. STUDY DESIGN: Computer simulations. ANIMALS: Five-year-old neutered male golden retriever (33 kg). METHODS: The EAI was implemented in a previously developed 3D CrCL-deficient canine pelvic limb computer simulation model. Ligament loads, relative tibial translation, and relative tibial rotation were determined and compared to the CrCL-intact and CrCL-deficient stifle. RESULTS: The EAI significantly increased peak caudal cruciate and medial collateral ligament loads, significantly changed when peak lateral collateral ligament load occurred, and did not significantly affect peak patellar ligament load compared to the CrCL-intact stifle. Compared to the CrCL-deficient stifle, peak caudal cruciate, lateral collateral, and medial collateral ligament loads significantly decreased in the EAI-managed stifle. Despite decreased peak caudal cruciate ligament loading, the EAI-managed stifle generated local maxima that exceeded those of the CrCL-deficient stifle at various intervals of stance. Peak relative tibial translation and rotation significantly decreased in the EAI-managed stifle compared to the CrCL-deficient stifle. CONCLUSION: Model-predicted stifle biomechanics differed after EAI system application in the CrCL-deficient stifle, but were not restored to that of the CrCL-intact stifle.

Canine Stifle Biomechanics Associated With Tibial Tuberosity Advancement Predicted Using a Computer Model.

OBJECTIVE: To evaluate the effects of tibial tuberosity advancement (TTA) on canine biomechanics in the cranial cruciate ligament (CrCL)-deficient stifle using a 3-dimensional quasi-static rigid body pelvic limb computer model simulating the stance phase of gait. STUDY DESIGN: Computer simulations. ANIMALS: A 5-year-old neutered male Golden Retriever weighing 33 kg. METHODS: A TTA was implemented in a previously developed canine pelvic limb computer model using the tibial plateau slope and common tangent planning techniques. Ligament loads, relative tibial translation, and relative tibial rotation were determined and compared to CrCL-intact and CrCL-deficient stifles. RESULTS: The TTA significantly decreased peak caudal cruciate ligament load, significantly increased peak lateral collateral ligament load, and significantly changed peak medial collateral ligament load occurrence, while there was no significant difference in peak patellar ligament load compared to the CrCL-intact stifle. Compared to the CrCL-deficient stifle, peak caudal cruciate, lateral collateral and medial collateral ligament loads significantly decreased, while peak patellar ligament load was similar, peak relative tibial translation significantly decreased and peak relative tibial rotation was converted to external rotation in the TTA-treated stifle. Each TTA planning technique generated similar caudal cruciate, medial collateral, and patellar ligament loading as well as relative tibial translation, but lateral collateral ligament loading and occurrence of relative tibial rotation differed significantly across the techniques. CONCLUSIONS: Model-predicted stifle ligament loads improved following TTA compared to the CrCL-deficient stifle, but TTA did not restore CrCL-intact stifle biomechanics. The TTA effectively reduced tibial translation, but tibial rotation was not stabilized.

Development of a Canine Rigid Body Musculoskeletal Computer Model to Evaluate Gait.

BACKGROUND: Kinematic and kinetic analysis have been used to gain an understanding of canine movement and joint loading during gait. By non-invasively predicting muscle activation patterns and forces during gait, musculoskeletal models can further our understanding of normal variability and muscle activation patterns and force profiles characteristic of gait. METHODS: Pelvic limb kinematics and kinetics were measured for a 2 year old healthy female Dachshund (5.4 kg) during gait using 3-D motion capture and force platforms. A computed tomography scan was conducted to acquire pelvis and pelvic limb morphology. Using the OpenSim modeling platform, a bilateral pelvic limb subject-specific rigid body musculoskeletal computer model was developed. This model predicted muscle activation patterns, muscle forces, and angular kinematics and joint moments during walking. RESULTS: Gait kinematics determined from motion capture matched those predicted by the model, verifying model accuracy. Primary muscles involved in generating joint moments during stance and swing were predicted by the model: at mid-stance the adductor magnus et brevis (peak activation 53.2%, peak force 64.7 N) extended the hip, and stifle flexor muscles (biceps femoris tibial and calcaneal portions) flexed the stifle. Countering vertical ground reaction forces, the iliopsoas (peak activation 37.9%, peak force 68.7 N) stabilized the hip in mid-stance, while the biceps femoris patellar portion stabilized the stifle in mid-stance and the plantar flexors (gastrocnemius and flexor digitorum muscles) stabilized the tarsal joint during early stance. Transitioning to swing, the iliopsoas, rectus femoris and tensor fascia lata flexed the hip, while in late swing the adductor magnus et brevis impeded further flexion as biceps femoris tibial and calcaneal portions stabilized the stifle for ground contact. CONCLUSION: The musculoskeletal computer model accurately replicated experimental canine angular kinematics associated with gait and was used to predict muscle activation patterns and forces. Thus, musculoskeletal modeling allows for quantification of measures such as muscle forces that are difficult or impossible to measure in vivo.

Effect of wheelchair headrest use on pediatric head and neck injury risk outcomes during rear impact.

Comparative risks or benefits to wheelchair-seated pediatric occupants in motor vehicles associated with wheelchair headrest use during rear impact were evaluated using pediatric head and neck injury outcome measures. A Hybrid III 6-year-old anthropomorphic test device (ATD), seated in identical WC19-compliant pediatric manual wheelchairs, was used to measure head and neck response during a 25 km/h (16 mph), 11 g rear impact. ATD responses were evaluated across two test scenarios: three sled tests conducted without headrests, and three with slightly modified commercial headrests. Head and neck injury outcomes measures included: linear head acceleration, head injury criteria (HIC) values, neck injury criteria (N(ij)) values, and combined rotational head velocity and acceleration. Neck and head injury outcome measures improved by 34-70% in sled tests conducted with headrests compared to tests without headrests. Headrest use reduced N(ij) values and the likelihood of concussion from values above established injury thresholds to values below injury thresholds. Injury measure outcome reductions suggest lower head and neck injury risks for wheelchair-seated children using wheelchair-mounted headrests as compared to non-headrest users in rear impact. Use of relative comparisons across two test scenarios served to minimize effects of ATD biofidelity limitations.

Transportation safety standards for wheelchair users: a review of voluntary standards for improved safety, usability, and independence of wheelchair-seated travelers.

Safe transportation for wheelchair users who do not transfer to the vehicle seat when traveling in motor vehicles requires after-market wheelchair tiedown and occupant restraint systems (WTORS) to secure the wheelchair and provide crashworthy restraint for the wheelchair-seated occupant. In the absence of adequate government safety standards, voluntary standards for the design and performance of WTORS, and for wheelchairs used as seats in motor vehicles, have been developed. The initial versions of these standards qualify equipment for use in all types and sizes of motor vehicles using a 30-mph (48-kph), 20-g frontal sled-impact test. The wheelchair standard requires four accessible, crash-tested securement points on wheelchairs so they can be more easily and effectively secured using a four-point strap-type tie-down system. Future voluntary standards are aimed at reducing injury risk for wheelchair-seated occupants in rear impacts and at providing a method for evaluating the crashworthiness of wheelchair seating systems independent of wheelchair base-frames. They also address improved usability and independence for wheelchair-seated travelers using public transportation by specifying universal docking interface geometry for wheelchairs and design and performance requirements for rear-facing wheelchair passenger stations for use in the very low-g environments of large fixed-route transit buses.

A three dimensional multiplane kinematic model for bilateral hind limb gait analysis in cats.

BACKGROUND: Kinematic gait analysis is an important noninvasive technique used for quantitative evaluation and description of locomotion and other movements in healthy and injured populations. Three dimensional (3D) kinematic analysis offers additional outcome measures including internal-external rotation not characterized using sagittal plane (2D) analysis techniques. METHODS: The objectives of this study were to 1) develop and evaluate a 3D hind limb multiplane kinematic model for gait analysis in cats using joint coordinate systems, 2) implement and compare two 3D stifle (knee) prediction techniques, and 3) compare flexion-extension determined using the multiplane model to a sagittal plane model. Walking gait was recorded in 3 female adult cats (age = 2.9 years, weight = 3.5 ± 0.2 kg). Kinematic outcomes included flexion-extension, internal-external rotation, and abduction-adduction of the hip, stifle, and tarsal (ankle) joints. RESULTS: Each multiplane stifle prediction technique yielded similar findings. Joint angles determined using markers placed on skin above bony landmarks in vivo were similar to joint angles determined using a feline hind limb skeleton in which markers were placed directly on landmarks ex vivo. Differences in hip, stifle, and tarsal joint flexion-extension were demonstrated when comparing the multiplane model to the sagittal plane model. CONCLUSIONS: This multiplane cat kinematic model can predict joint rotational kinematics as a tool that can quantify frontal, transverse, and sagittal plane motion. This model has multiple advantages given its ability to characterize joint internal-external rotation and abduction-adduction. A further, important benefit is greater accuracy in representing joint flexion-extension movements.

Wheelchair tiedown and occupant restraint system issues in the real world and the virtual world: combining qualitative and quantitative research approaches.

The Americans with Disabilities Act requires that transit providers accommodate passengers who use "common wheelchairs" when traveling in a motor vehicle. Wheelchair tiedown and occupant restraint systems are commonly used to secure wheelchairs and restrain occupants in fixed-route and demand route transit vehicles. Throughout the 17 years since the Americans with Disabilities Act has been in effect, transit providers have complained about the usability of wheelchair tiedown and occupant restraint systems, and improper securement has been linked to injuries among wheelchair users during "nonimpact incidents." This research study explored the use of wheelchair tiedown and occupant restraint systems in actual practice and the potential risks of misuse to wheelchair-seated individuals. The qualitative research conducted in this study revealed that improper wheelchair securement (i.e. using less than four tiedown straps) can be fairly common practice in fixed-route transit. In addition, preliminary computer simulations show that improper wheelchair securement in emergency driving conditions may place wheelchair occupants at a greater risk of injury. It should be noted, however, that this is a pilot study and has its limitations. For example, qualitative data were gathered from one metropolitan area transit provider across a limited range of vehicle and wheelchair types. Additionally, the computer simulation model used in this study was originally validated for impact situations.

Riding a bus while seated in a wheelchair: A pilot study of attitudes and behavior regarding safety practices.

A total of 283 wheelchair-seated bus riders responded to a 35-item Web-based survey investigating their experiences on public, fixed-route buses. The survey addressed the use of wheelchair tiedowns and occupant restraint systems (WTORS), the attitudes and behaviors of wheelchair users toward the use of this equipment, and the transit experience. Results indicate that consistent use of four-point tiedown and occupant restraint systems is fairly low. Only 33.2% of the participants reported always securing their wheelchair, and 62.2% reported using occupant restraints consistently. A preference for fixed-route over para-transit was related to larger city size. Implementation of transit agency policy regarding WTORS was found to be inconsistent. Easier-to-use WTORS and improved operator training in larger transit agencies would likely increase the correct use of safety equipment and improve wheelchair users' bus-riding experiences.

Why Owners Choose an Orthosis Over Stifle Surgery for Canine Cranial Cruciate Ligament Deficiency.

The objective of this study was to describe the patient population of dogs with cranial cruciate ligament (CrCL) deficiency that were prescribed a stifle orthosis. A total of 215 client-owned dogs with previously diagnosed CrCL deficiency were prescribed a stifle orthosis at a veterinary pain management and mobility clinic. Patient intake data collected included dog signalment, chief medical complaint, home environment and activity description, medical and surgical history, and diagnosing veterinarian. An orthopedic examination was conducted to assess pelvic limb function and determine pelvic limb morphologic measures. Spayed females (57.2%) were most common in our sample. Median age, body weight, and body condition score were 9.00 ± 3.23 years, 32.98 ± 13.37kg, and 6.00 ± 1.04, respectively. Most common breeds prescribed stifle orthoses included Labrador Retriever, Golden Retriever, and German Shepherd. Right and left limbs were equally affected, and 19.5% of dogs previously had stifle stabilization surgery. Primary reasons for seeking a stifle orthosis consultation were surgical concerns, advanced age, and surgery cost. Most common chief complaints included altered gait, decreased weight bearing, and pain following activity. Reduced stifle extension, increased cranial drawer score, and decreased 3-leg stance time characterized the CrCL-deficient stifle. Stifle orthosis represents an alternative approach to surgical stabilization and management of CrCL deficiency. CrCL-deficient dogs prescribed stifle orthoses were generally large breeds of advanced age with above ideal body condition score. Owners commonly sought a stifle orthosis for CrCL deficiency due to reservations regarding surgical management.

Biomechanics of an orthosis-managed cranial cruciate ligament-deficient canine stifle joint predicted by use of a computer model.

OBJECTIVE To evaluate effects of an orthosis on biomechanics of a cranial cruciate ligament (CrCL)-deficient canine stifle joint by use of a 3-D quasistatic rigid-body pelvic limb computer model simulating the stance phase of gait and to investigate influences of orthosis hinge stiffness (durometer). SAMPLE A previously developed computer simulation model for a healthy 33-kg 5-year-old neutered Golden Retriever. PROCEDURES A custom stifle joint orthosis was implemented in the CrCL-deficient pelvic limb computer simulation model. Ligament loads, relative tibial translation, and relative tibial rotation in the orthosis-stabilized stifle joint (baseline scenario; high-durometer hinge]) were determined and compared with values for CrCL-intact and CrCL-deficient stifle joints. Sensitivity analysis was conducted to evaluate the influence of orthosis hinge stiffness on model outcome measures. RESULTS The orthosis decreased loads placed on the caudal cruciate and lateral collateral ligaments and increased load placed on the medial collateral ligament, compared with loads for the CrCL-intact stifle joint. Ligament loads were decreased in the orthosis-managed CrCL-deficient stifle joint, compared with loads for the CrCL-deficient stifle joint. Relative tibial translation and rotation decreased but were not eliminated after orthosis management. Increased orthosis hinge stiffness reduced tibial translation and rotation, whereas decreased hinge stiffness increased internal tibial rotation, compared with values for the baseline scenario. CONCLUSIONS AND CLINICAL RELEVANCE Stifle joint biomechanics were improved following orthosis implementation, compared with biomechanics of the CrCL-deficient stifle joint. Orthosis hinge stiffness influenced stifle joint biomechanics. An orthosis may be a viable option to stabilize a CrCL-deficient canine stifle joint.

Pilot study of safety belt usability for vehicle occupants seated in wheelchairs.

This study investigates the usability of wheelchair occupant restraint systems (WORS) that are used for crash protection of individuals seated in wheelchairs during motor vehicle transit. Ten independent adults with significant functional limitations who use wheelchairs for primary mobility were observed and interviewed while performing reach and manipulation tasks associated with WORS usage. Participants' opinions on ease of use and comfort-related factors were obtained for four occupant restraint scenarios. The study results show evidence of user problems with common WORS designs for use by wheelchair-seated individuals with significant functional limitations. Results from this pilot study suggest redesign of latch plates and buckles used in WORS to enable wheelchair-seated individuals with functional limitations to don and buckle belt restraints more easily and independently. Additionally, this study provides guidance to occupant-restraint manufacturers and wheelchair designers regarding belt-restraint usability. Improved WORS usability will complement other efforts to increase frequency of safety belt usage and lead to improved occupant safety.

Influence of biomechanical parameters on cranial cruciate ligament-deficient or -intact canine stifle joints assessed by use of a computer simulation model.

OBJECTIVE To investigate the influence of 4 biomechanical parameters on canine cranial cruciate ligament (CrCL)-intact and -deficient stifle joints. SAMPLE Data for computer simulations of a healthy 5-year-old 33-kg neutered male Golden Retriever in a previously developed 3-D rigid body pelvic limb computer model simulating the stance phase during walking. PROCEDURES Canine stifle joint biomechanics were assessed when biomechanical parameters (CrCL stiffness, CrCL prestrain, body weight, and stifle joint friction coefficient) were altered in the pelvic limb computer simulation model. Parameters were incrementally altered from baseline values to determine the influence on stifle joint outcome measures (ligament loads, relative tibial translation, and relative tibial rotation). Stifle joint outcome measures were compared between CrCL-intact and -deficient stifle joints for the range of parameters evaluated. RESULTS In the CrCL-intact stifle joint, ligament loads were most sensitive to CrCL prestrain. In the CrCL-deficient stifle joint, ligament loads were most sensitive to body weight. Relative tibial translation was most sensitive to body weight, whereas relative tibial rotation was most sensitive to CrCL prestrain. CONCLUSIONS AND CLINICAL RELEVANCE In this study, computer model sensitivity analyses predicted that CrCL prestrain and body weight influenced stifle joint biomechanics. Cranial cruciate ligament laxity may influence the likelihood of CrCL deficiency. Body weight could play an important role in management of dogs with a CrCL-deficient stifle joint.

Using test dummy experiments to investigate pediatric injury risk in simulated short-distance falls.

BACKGROUND: Short-distance falls, such as from a bed, are often falsely reported scenarios in child abuse. In attempting to differentiate between abusive and nonabusive injury, knowledge of factors that affect injury risk in falls could prove useful. OBJECTIVES: To assess the biomechanics associated with simulated short-distance falls in children (one fall scenario, without attempting to maximize injury potential) and to investigate the effect of impact surface type on injury risk. METHODS: Repeatable fall experiments from bed height (0.68 m) onto different surfaces were conducted using an instrumented side-lying Hybrid II 3-year-old test dummy. Biomechanical measures assessed in falls included head acceleration, pelvis acceleration, femur loading, and head injury criteria. RESULTS: Fall dynamics resulted in the pelvis or legs making first contact. Biomechanical measures assessed in simulated bed falls were below known head injury criteria and lower extremity injury thresholds. The impact surface type had a significant effect on head injury risk and lower extremity loading. Playground foam proved to have the lowest associated injury risk of all the tested surfaces. CONCLUSIONS: The biomechanics of a child falling from a short distance, such as from a bed, were investigated using an experimental laboratory mock-up and an instrumented test dummy. Despite the impact surface having an effect on injury risk, rolling from a 0.68-m (27-in) horizontal surface from a side-lying posture presented low risk of contact-type head injury and leg injury on all tested impact surfaces.

Injury biomechanics for aiding in the diagnosis of abusive head trauma.

Much of what is understood as potential for injury is based in what has been observed clinically. This knowledge base is critical for decision making but has inherent and important limitations. Experimental studies investigating the influence of environmental factors, such as height of fall and surface type on injury potential, add important information, but also have inherent limitations. Important trends and predictions of probable injury can be studied but inference to a specific child's injuries is difficult because of unaccounted for contributing factors of injury risk. Such factors include muscle contraction, protective reflexes, and specific tissue response to trauma forces. Additional biomechanical research is needed to bridge the gap between clinical observations and experimental predictions. The specific and unique perspective of the neurosurgeon is a critical piece in differentiating accidental and nonaccidental head injury with experience and reason as the basis of the conclusion. Do the physics of the injury match the mechanistic principals of the described injury event? Could all of the injuries result from the event? Is it plausible that these set of injuries occurred from the described event based on the [table: see text] physician's experience and the current scientific understanding of injury biomechanics? Do the mechanical forces of the reported mechanism and injuries match? To determine that an explanation is plausible requires consideration of all the facts and injuries, consideration of the described behavior, and consistency with the neurologic status. These facts of the case are compared with medical knowledge and the learned experience of the neurosurgeon. The answer to the question "is it possible?" is based on clinical experience and objective reasoning. Rather than a black box question and answer based in unrealistic probability, the answer is based on the facts of the case and physical principles that govern biomechanics and resultant injuries.

Preliminary evaluation of wheelchair occupant restraint system usage in motor vehicles.

Individuals using wheeled mobility devices (WMDs) often use them as motor vehicle seats during transportation. Wheelchair occupant restraint systems (WORSs), consisting of upper torso and pelvic restraints, are usually mounted to the structure of transit vehicles to secure individuals within their wheelchair seats. This preliminary study attempts to evaluate the use and satisfaction of currently installed vehicle-mounted WORSs for individuals using WMD as seats in motor vehicles. A survey was conducted among 33 adults who use their WMD to travel in motor vehicles. Results from the survey showed that upper torso and pelvic restraints installed in private vehicles are quick, comfortable, and easy to use. However, WORS installed in mass transit and paratransit are often uncomfortable to wear, difficult to reach, and time-consuming to use. This preliminary study documents the growing need for developing alternative WORS that are safe, comfortable, and that allow independent usage for wheelchair occupants while traveling in a motor vehicle.

Wheelchair caster loading during frontal impact.

Many wheelchair users are required or choose to use their wheelchairs as a motor vehicle seat during transport. It is therefore key that the wheelchair components be designed to tolerate crash-level loading conditions. Casters are particularly prone to failure under crash loading conditions. Our study evaluated wheelchair caster loading during 20g/48 kph frontal sled impact testing using an 85-kg surrogate wheelchair base (SWCB) with casters positioned on a load-measuring platform. A Hybrid III 50th percentile male test dummy was seated in the SWCB, which simulated a power wheelchair and was secured using four-point tiedowns. Various rear securement point heights and wheelchair seating systems were used to study their effect on caster loading. Caster normal loading was found to vary from 769 to 7,209 N depending on rear securement location and integrity of the seating system. Dynamic sled impact test results showed that normal loading of the front wheelchair casters was influenced by wheelchair seating system integrity and rear wheelchair securement height. Shear loading varied from 781 to 1,589 N and did not appear to be dependent on seat integrity or rear securement height. The load/time histories measured during dynamic impact testing can be used to guide the development of transit-safe caster design.

Wheelchair seating: a state of the science report.

Regardless of the field, agenda-setting processes are integral to establishing research and development priorities. Beginning in 1998, the National Institute on Disability and Rehabilitation Research mandated that each newly funded Rehabilitation Engineering and Research Center (RERC) hold a state-of-the-science consensus forum during the third year of its 5-year funding cycle. NIDRR's aim in formalizing this agenda-setting process was to facilitate the formulation of future research and development priorities for each respective RERC. In February 2001, the RERC on Wheeled Mobility, University of Pittsburgh, conducted one of the first such forums. The scope encompassed both current scientific knowledge and clinical issues. In preparation, expert interviews were carried out to establish the focus for the forum. Because a stakeholder forum on wheelchair technology had recently been held, opinion favored wheelchair seating as the focus and included the following core areas: seating for use in wheelchair transportation, seated postural control, seating discomfort, and tissue integrity management. The aim of this report is to present a summary of the workshop outcomes, describe the process, and increase awareness of this agenda-setting process in order to enhance future participation in a process that critically influences the field of wheeled mobility.

Canine stifle joint biomechanics associated with tibial plateau leveling osteotomy predicted by use of a computer model.

OBJECTIVE: To evaluate effects of tibial plateau leveling osteotomy (TPLO) on canine stifle joint biomechanics in a cranial cruciate ligament (CrCL)-deficient stifle joint by use of a 3-D computer model simulating the stance phase of gait and to compare biomechanics in TPLO-managed, CrCL-intact, and CrCL-deficient stifle joints. SAMPLE: Computer simulations of the pelvic limb of a Golden Retriever. PROCEDURES: A previously developed computer model of the canine pelvic limb was used to simulate TPLO stabilization to achieve a tibial plateau angle (TPA) of 5° (baseline value) in a CrCL-deficient stifle joint. Sensitivity analysis was conducted for tibial fragment rotation of 13° to -3°. Ligament loads, relative tibial translation, and relative tibial rotation were determined and compared with values for CrCL-intact and CrCL-deficient stifle joints. RESULTS: TPLO with a 5° TPA converted cranial tibial translation to caudal tibial translation and increased loads placed on the remaining stifle joint ligaments, compared with results for a CrCL-intact stifle joint. Lateral collateral ligament load was similar, medial collateral ligament load increased, and caudal cruciate ligament load decreased after TPLO, compared with loads for a CrCL-deficient stifle joint. Relative tibial rotation after TPLO was similar to that of a CrCL-deficient stifle joint. Stifle joint biomechanics were affected by TPLO fragment rotation. CONCLUSIONS AND CLINICAL RELEVANCE: In the model, stifle joint biomechanics were partially improved after TPLO, compared with CrCL-deficient stifle joint biomechanics, but TPLO did not fully restore CrCL-intact stifle joint biomechanics. Overrotation of the tibial fragment negatively influenced stifle joint biomechanics by increasing caudal tibial translation.

Evaluation of varying morphological parameters on the biomechanics of a cranial cruciate ligament-deficient or intact canine stifle joint with a computer simulation model.

OBJECTIVE: To investigate the influence of varying morphological parameters on canine stifle joint biomechanics by use of a 3-D rigid-body canine pelvic limb computer model that simulated an intact and cranial cruciate ligament (CrCL)-deficient stifle joint across the stance phase of gait at a walk. SAMPLE: Data from computer simulations. PROCEDURES: Computer model morphological parameters, including patellar ligament insertion location, tibial plateau angle (TPA), and femoral condyle diameter (FCD), were incrementally altered to determine their influence on outcome measures (ligament loads, relative tibial translation, and relative tibial rotation) during simulation of the stance phase of gait at a walk. Outcome measures were assessed for each scenario and compared between an intact and CrCL-deficient stifle joint with the sensitivity index (the percentage change in outcome measure divided by the percentage change in input parameter). RESULTS: In a CrCL-intact stifle joint, ligament loads were most sensitive to TPA. In a CrCL-deficient stifle joint, outcome measures were most sensitive to TPA with the exception of caudal cruciate ligament and lateral collateral ligament loads, which were sensitive to FCD and TPA. Relative tibial translation was sensitive to TPA and patellar ligament insertion location, whereas relative tibial rotation was most sensitive to TPA. CONCLUSIONS AND CLINICAL RELEVANCE: The computer model sensitivity analyses predicted that individual parameters, particularly TPA and FCD, influence stifle joint biomechanics. Therefore, tibial and femoral morphological parameters may affect the likelihood, prevention, and management of CrCL deficiency.